Surgical stapler

ABSTRACT

A surgical device is described herein that can be used to fire different types and sizes of disposable loading units. In a preferred embodiment, the device applies parallel rows of surgical fasteners to body tissue and concomitantly forms an incision between the rows of staples during an endoscopic or laparoscopic surgical procedure. The device can be utilized with disposable loading units configured to apply linear rows of staples measuring from about 15 mm in length to about 60 mm in length and can be used to fire disposable loading units containing surgical clips and individual staples.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 11/011,355 filed Dec. 14, 2004 which is a continuation of Ser. No.09/625,886 filed Jul. 26, 2000, which is a continuation of Ser. No.09/497,647 filed Feb. 3, 2000, which is a continuation of Ser. No.09/119,543 filed Jul. 20, 1998, which is a continuation of Ser. No.08/546,253 filed Oct. 20, 1995, which is a continuation-in-part of Ser.No. 08/520,202 filed on Aug. 28, 1995 now U.S. Pat. No 5,762,256. Eachof which is incorporated herein by reference in their entirety.

BACKGROUND

1. Technical Field

This application relates to a surgical stapling apparatus, and moreparticularly, to an apparatus for sequentially applying a plurality ofsurgical fasteners to body tissue and optionally incising the fastenedtissue.

2. Background of Related Art

Surgical devices wherein tissue is first grasped or clamped betweenopposing jaw structure and then joined by surgical fasteners are wellknown in the art. In some instruments a knife is provided to cut thetissue which has been joined by the fasteners. The fasteners aretypically in the form of surgical staples but two part polymericfasteners can also be utilized.

Instruments for this purpose can include two elongated members which arerespectively used to capture or clamp tissue. Typically, one of themembers carries a staple cartridge which houses a plurality of staplesarranged in at least two lateral rows while the other member has ananvil that defines a surface for forming the staple legs as the staplesare driven from the staple cartridge. Generally, the stapling operationis effected by cam bars that travel longitudinally through the staplecartridge, with the cam bars acting upon staple pushers to sequentiallyeject the staples from the staple cartridge. A knife can travel betweenthe staple rows to longitudinally cut and/or open the stapled tissuebetween the rows of staples. Such instruments are disclosed, forexample, in U.S. Pat. No. 3,079,606 and U.S. Pat. No. 3,490,675.

A later stapler disclosed in U.S. Pat. No. 3,499,591 applies a doublerow of staples on each side of the incision. This is accomplished byproviding a disposable loading unit in which a cam member moves throughan elongate guide path between two sets of staggered staple carryinggrooves. Staple drive members are located within the grooves and arepositioned in such a manner so as to be contacted by the longitudinallymoving cam to effect ejection of the staples from the staple cartridgeof the disposable loading unit. Other examples of such staplers aredisclosed in U.S. Pat. Nos. 4,429,695 and 5,065,929.

Each of the instruments described above were designed for use inconventional surgical procedures wherein surgeons have direct manualaccess to the operative site. However, in endoscopic or laparoscopicprocedures, surgery is performed through a small incision or through anarrow cannula inserted through small entrance wounds in the skin. Inorder to address the specific needs of endoscopic and/or laparoscopicsurgical procedures, endoscopic surgical stapling devices have beendeveloped and are disclosed in, for example, U.S. Pat. No. 5,040,715(Green, et al.); U.S. Pat. No. 5,307,976 (Olson, et al.); U.S. Pat. No.5,312,023 (Green, et al.); U.S. Pat. No. 5,318,221 (Green, et al.); U.S.Pat. No. 5,326,013 (Green, et al.); and U.S. Pat. No. 5,332,142(Robinson, et al.).

U.S. Surgical, the assignee of the present application, has manufacturedand marketed endoscopic stapling instruments, such as the Multifire ENDOGIA* 30 and Multifire ENDO GIA* 60 instruments, for several years. Theseinstruments have provided significant clinical benefits. Nonetheless,improvements are possible, for example, by reducing the cost andcomplexity of manufacture.

Current laparoscopic linear stapling devices are configured to operatewith disposable loading units (U.S. Surgical) and staple cartridges(Ethicon) of only one size. For example, individual linear staplers arepresently available for applying parallel rows of staples measuring 30mm, 45 mm and 60 mm in length. Thus, during a normal operation, asurgeon may be required to utilize several different staplinginstruments to perform a single laparoscopic surgical procedure. Suchpractices increase the time, complexity and overall costs associatedwith laparoscopic surgical procedures. In addition, costs are greater indesigning and manufacturing multiple stapler sizes, as opposed tocreating a single, multipurpose stapler.

It would be extremely beneficial to provide a surgical device for useduring laparoscopic and/or endoscopic surgical procedures that can beemployed with several different sized disposable loading units to reducethe overall costs associated with such procedures. It would also beparticularly beneficial if the device could perform multiple tasks,using disposable loading units of varying size and of varying purpose,such as, for example, to staple, clip and/or cut.

In making improvements or modifications to the current instruments, itwould be highly desirable not to sacrifice any of the important benefitsof the MULTIFIRE ENDO GIA* 30 and 60 instruments as compared to othercommercially available products, e.g., the endoscopic staplinginstruments manufactured and marketed by Ethicon, Inc. For example, anyimprovement should advantageously provide a fresh knife blade for eachfiring of the instrument and ensure that the disposable loading unit issecurely retained in the stapling instrument unless and until theoperating team chooses to remove it. These advantages have historicallybeen found in the U.S. Surgical instruments, but not in the Ethiconinstruments.

Therefore, a need exists for a reliable surgical stapler and disposableloading units for use therewith that exhibit all of the benefits of thepresent assignee's commercially available instruments while alsoreducing the cost and complexity of manufacture.

The subject application is primarily directed to a stapling device forapplying parallel rows of surgical fasteners to body tissue and,preferably, one that concomitantly forms an incision between the rows ofstaples during an endoscopic or laparoscopic surgical procedure. Aparticularly unique feature of the stapling device described herein isthat it can be employed with a number of different disposable loadingunits. Moreover, the stapling device of the subject application can beutilized with disposable loading units configured to apply linear rowsof staples measuring from about 15mm in length to about 60mm in length.

In a preferred embodiment of the subject surgical stapler, the deviceincludes a handle assembly including an elongated barrel portion and anactuation handle movable through an actuating stroke, and an elongatedbody extending distally from the barrel portion of the handle assemblyand defining a longitudinal axis. An elongated actuation shaft issupported at least in part within the barrel portion of the handleassembly and it has a particular linear dimension. The actuation handleinteracts with the actuation shaft such that manipulation of theactuation handle through a complete actuating stroke causes theactuation shaft to translate through a predetermined linear distance.

A disposable loading unit is operatively engaged in a distal portion ofthe elongated body. The disposable loading unit preferably includes acarrier, a staple cartridge containing a plurality of staples, anactuator (movable through the housing and staple cartridge) and ananvil. The instrument actuation shaft drives the actuator through thestaple cartridge to eject the staples against the anvil to form a stapleline having a particular linear dimension. Preferably, the lineardimension of the staple line corresponds to the distance through whichthe actuation shaft translates in response to manipulation of theactuation handle through a particular number of complete or partialactuation strokes numbering more than one complete stroke.

The actuation shaft is preferably defined at least in part by a toothedrack having a particular rack length, and the actuation handle has apawl member for selectively engaging the toothed rack and advancing theactuation shaft in response to manipulation of the actuation handle.When a disposable loading unit having linear rows of staples is used,the linear dimension of the staple line applied by the stapling unit ispreferably proportional to the longitudinal travel of the actuationshaft. In a most preferred embodiment, the minimum linear dimension ofthe staple line will always be greater than the maximum linear distancethrough which the actuation shaft translates in response to a completeactuation stroke.

When a disposable loading unit having an anvil is used, the actuationhandle is preferably movable through a clamping stroke in which theactuation shaft translates through a predetermined clamping distance tomove the anvil from an open position to a closed position. The clampingstroke precedes the first of any number of complete or partial actuationstrokes. In a preferred embodiment, an engagement hook is mounted withinthe barrel portion of the handle assembly to selectively maintain theactuation shaft in a particular position after traveling through theclamping distance and a notch is defined in a distal end portion of theactuation shaft, distal of the toothed rack, for receiving andreleasably retaining the engagement hook.

In use of a preferred embodiment, movement of the actuation handle in adirection opposite the clamping stroke causes the engagement hook torelease the actuation shaft, permitting the anvil to move to an openposition. A lift finger is provided on a flange extending from theactuation handle and is positioned to move the engagement hook out ofengagement with the notch when the actuation handle is moved in adirection opposite the clamping stroke. Preferably, a first biasingspring is provided within the handle assembly for biasing the actuationhandle in a clockwise direction and a second biasing spring is providedwithin the handle assembly for biasing the actuation handle in acounter-clockwise direction, about a handle pivot point. Thecounter-clockwise direction corresponds to the direction of the clampingand actuating strokes.

The engagement hook is preferably configured to interact with thetoothed rack to maintain the actuation shaft in a particular linearposition during an actuation stroke, and it is normally biased intoengagement with the actuation shaft. An abutment strut or beam isoperatively associated with a proximal end portion of the stapler bodyfor maintaining the engagement hook in a position out of engagement withthe actuation shaft until a disposable loading unit is operativelyengaged in a distal end portion of the elongated body. The abutmentstrut permits the engagement hook to engage the actuation shaft after adisposable loading unit has been operatively engaged in a distal endportion of the elongated instrument body.

In another preferred embodiment of the surgical stapling apparatusdisclosed herein, a release mechanism is operatively associated with thehandle assembly for effectuating the manual disengagement of theengagement hook from the actuation shaft to permit subsequent distaladvancement of the actuation shaft in response to manipulation of theactuation handle through any number of subsequent stapling strokes. Inaddition, a retracting mechanism is operatively associated with thehandle assembly for effectuating the manual retraction of the actuationshaft at any point in the actuating stroke so that the actuator can bewithdrawn to permit the anvil to move from a closed position to an openposition.

In a preferred embodiment of the device described herein, the disposableloading unit is a adapted to apply linear rows of staples and includes:a carrier having a proximal end portion including a coupling forreleasable engagement in a distal end portion of the elongatedinstrument body; an elongate staple cartridge supported in the carrierand containing a plurality of surgical fasteners and a plurality offastener pushers for ejecting the fasteners from the staple cartridge;an actuator for contacting the fastener pushers; and an anvil supportedon the carrier and mounted for movement with respect to the staplecartridge between an open position and a closed position. The anvilpreferably has a fastener forming surface against which the surgicalfasteners are driven when ejected from the staple cartridge by thefastener pushers, and a camming surface opposite the fastener formingsurface. The actuator is preferably wedged actuator that translatesthrough the staple cartridge to sequentially interact with the fastenerpushers to eject the fasteners from the staple cartridge.

The disposable loading unit further preferably includes an elongateddrive beam having a proximal engagement portion, a distal working endportion having an abutment surface and a camming member. The proximalengagement portion is configured to mate with a distal end portion ofthe actuation assembly of the stapler while the abutment surface engagesthe actuator to eject staples from the staple cartridge during firing.The camming member contacts the camming surface of the anvil duringfiring. In use, the stapler actuation assembly moves the drive beamthrough the carrier causing the camming member to close the anvil ormaintain the anvil closed as it substantially simultaneously causes theactuator to translate through the staple cartridge, thereby sequentiallyinteracting with the plurality of fastener pushers to fire the staples.

Preferably, the camming member is defined by a cylindrical cam rollermounted on a flange extending from the distal working end portion of thedrive beam. A longitudinal slot is defined in the anvil to accommodatethe linear translation of the working end portion of the drive beam, anda transverse support flange is operatively mounted on the working endportion opposite the cam roller to engage an undersurface of the carrieras the cam roller engages the camming surface of the anvil. Alongitudinal slot is also defined in the undersurface of the carrier toaccommodate the linear translation of the working end portion of thedrive beam. An optional anvil cover can be provided to ensure tissue isnot inadvertently contacted by the drive beam or cam roller duringfiring.

Preferably, a knife blade is operatively supported adjacent a leadingedge of the working end portion of the drive beam for forming anincision in stapled body tissue. Also, the actuator is preferably a sledincluding a planar base portion and a plurality of spaced apartupstanding cam wedges each having an inclined leading edge forinteracting with the fastener pushers within the staple cartridge.

In a preferred embodiment of the stapling device described herein, thedistal end portion of the elongated body and the proximal portion of thecarrier includes cooperating portions of a bayonet-type coupling. Thecoupling facilitates the convenient removal and engagement of a varietyof different sized disposable loading units including those which areconfigured to apply staple rows that are approximately 30 mm in length,45 mm in length, and 60 mm in length. Accordingly, it is envisioned thatthe device can be sold and marketed as a kit which would include atleast one surgical instrument designed to actuate compatible disposableloading units and a plurality of disposable loading units that can varyin size and type. The disposable loading units can be adapted to applylinear rows of staples, clips or other forms of fasteners. A commonfeature of these disposable loading units is that they utilize thelongitudinal motion of the instrument actuation control rod to apply thefasteners.

These and other features of the surgical stapling device of the subjectapplication will become more readily apparent to those skilled in theart from the following detailed description of the preferred embodimentsof the device taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the surgical stapling apparatus of the subjectapplication will be described hereinbelow with reference to the drawingswherein:

FIG. 1 is a perspective view of a surgical stapling apparatusconstructed in accordance with a preferred embodiment of the subjectapplication in conjunction with three different sized disposable loadingunits each configured for utilization with the stapling apparatus;

FIG. 2 is an exploded perspective view of the handle assembly of thesurgical stapling apparatus illustrated in FIG. 1;

FIG. 3 is an exploded perspective view of a disposable loading unitconstructed in accordance with a preferred embodiment of the subjectapplication;

FIG. 4 is a perspective view in partial cross-section of the handleassembly and body portion of the stapling apparatus illustrated in FIG.1 as the disposable loading unit of FIG. 3 is inserted into the distalend of the body;

FIG. 5 is a perspective view which corresponds to the illustration inFIG. 4 with the disposable loading unit mounted in the body of thestapling apparatus and the actuation mechanism within the handle portionenabled as a result of the insertion of the disposable loading unit;

FIG. 6 is a side elevational view of the surgical stapling apparatus ofthe subject application with the handle portion sectioned to illustratethe relative positions of the components of the actuation assemblyhoused therein prior to actuation;

FIGS. 7 is a side elevational view of the surgical stapling apparatus ofthe subject application with the handle portion sectioned to illustratethe relative positions of the components of the actuation assembly whenthe actuation handle is partially compressed to move the anvil of thedisposable loading unit to a closed position;

FIG. 8 is a side elevational view of the surgical stapling apparatus ofthe subject application with the handle portion sectioned to illustratethe relative positions of the components of the actuation assembly whenthe actuation handle is released to permit the anvil of the disposableloading unit to move to an open position;

FIG. 9 is a side elevational view of the surgical stapling apparatus ofthe subject application with the handle portion sectioned to illustratethe relative positions of the components of the actuation assembly whenthe actuation handle is moved to a position wherein the anvil of thedisposable loading unit is maintained in an open position;

FIG. 10 is a side elevational view of the surgical stapling apparatus ofthe subject application with the handle portion sectioned to illustratethe relative positions of the components of the actuation assembly whenthe actuation handle is manipulated through one complete actuationstroke to apply a portion of the staples from the staple cartridge ofthe disposable loading unit to body tissue;

FIG. 11 is a side elevational view of the surgical stapling apparatus ofthe subject application with the handle portion sectioned to illustratethe relative positions of the components of the actuation assembly whenthe disposable loading unit is removed from the distal end of thestapler body;

FIG. 12 is a side elevational view of the disposable loading unit of thesubject application with the body thereof sectioned to illustrate therelative positions of the components prior to closing the anvil to clampa tubular vessel;

FIG. 13 is a side elevational view of the disposable loading unit of thesubject application with the body thereof sectioned to illustrate therelative positions of the components after the apparatus has beencompletely fired;

FIG. 14 is a side elevational view of the disposable loading unit asillustrated in FIG. 13 with the anvil moved to an open position underthe bias of a release spring;

FIG. 15 illustrates an alternate embodiment of a disposable loading unitadapted to apply surgical clips;

FIG. 16 illustrates an alternate embodiment of a disposable loading unitadapted to apply single surgical staples;

FIG. 17 is a perspective view of another surgical stapling apparatusconstructed in accordance with a preferred embodiment of the subjectinvention illustrated in conjunction with one of several different sizeddisposable loading units employed with the apparatus;

FIG. 18 is an exploded perspective view of the handle assembly of thesurgical stapling apparatus of FIG. 17 with the components associatedtherewith separated for ease of illustration;

FIG. 19 is an exploded perspective view of the body portion of thesurgical stapling apparatus of FIG. 17 in conjunction with the elongatedcontrol rod which extends therethrough;

FIG. 20 is a perspective view of a distal portion of the control rodillustrated in FIG. 19;

FIG. 21 is a cross-sectional view taken along line 21-21 of FIG. 19illustrating the proximal portion of the inner support tube housedwithin the body portion of the surgical stapling apparatus of FIG. 17;

FIG. 22 is a side elevational view in partial cross-section of thesurgical stapling apparatus of FIG. 17 illustrating the orientation ofthe rack lock prior to mounting the disposable loading unit in thedistal end of the body portion;

FIG. 23 is a side elevational view in partial cross-section of thesurgical stapling apparatus of FIG. 17 illustrating the orientation ofthe rack lock after the disposable loading unit has been mounted in thedistal end of the body portion;

FIG. 24 is an exploded perspective view of a disposable loading unitconstructed in accordance with a preferred embodiment of the subjectinvention which includes a lockout assembly that functions to limit thelongitudinal translation of the control shaft illustrated in FIGS. 19and 20;

FIG. 25 is an enlarged exploded perspective view of the lockout assemblyillustrated in FIG. 24 with a distal portion of the control rod;

FIG. 26 is a side elevational view in partial cross-section of aproximal portion of the disposable loading unit of FIG. 24 as it isinserted into the distal end of the body portion with the lockoutassembly disposed in a pre-actuated condition;

FIG. 27 is a side elevation view in partial cross-section of theproximal portion of the disposable loading unit of FIG. 24 when themounting portion thereof is fully inserted into the distal end of thebody portion;

FIG. 28 is a side elevational view in partial cross-section of theproximal portion of the disposable loading unit of FIG. 24 as it isrotated into an operational position;

FIG. 29 is a cross-sectional view taken along line 29-29 of FIG. 26illustrating the alignment of the notches in the head of the control rodand the engagement fingers at the proximal end of the axial driveassembly;

FIG. 30 is a cross-sectional view taken along line 30-30 of FIG. 28illustrating the position of the head of the control rod in relation tothe engagement fingers after the disposable loading unit has beenrotated into an operational position;

FIG. 31 is a side elevational view in partial cross-section of thesurgical stapling apparatus of FIG. 17 prior to a stapling procedurewith the anvil in an open position and the actuation shaft and toothedrack disposed in a proximal-most position within the handle assembly;

FIG. 32 is a side elevational view in partial cross-section of thesurgical stapling apparatus of FIG. 17 illustrating the actuation shaftand toothed rack advanced distally through a clamping stroke toeffectuate the movement of the anvil from the open position shown inFIG. 31 to a closed position;

FIG. 33 is a side elevational view in partial cross-section of thesurgical stapling apparatus of FIG. 17 illustrating the disengagement ofthe rack lock and pawl from the actuation shaft and toothed rack by theretraction mechanism to effectuate the movement of the anvil from theclosed position shown in FIG. 32 to an open position;

FIG. 34 corresponds to FIG. 32 and illustrates the surgical staplingapparatus with the anvil in a closed position after the actuation handlehas been manipulated through a clamping stroke;

FIG. 35 is a side elevational view in partial cross-section of thesurgical stapling apparatus of FIG. 17 illustrating the manual releaseof the rack lock to permit distal translation of the actuation shaftduring subsequent stapling strokes;

FIG. 36 is a side elevational view in partial cross-section of thesurgical stapling apparatus of FIG. 17 illustrating the actuation shaftand toothed rack advanced distally in response to a complete staplingstroke of the actuation handle to effectuate partial sequential ejectionof staples from the cartridge;

FIG. 37 is a side elevational view in partial cross-section of thesurgical stapling apparatus of FIG. 17 illustrating the actuation shaftand toothed rack advanced distally in response to a second completestapling stroke of the actuation handle to complete the sequentialejection of the staples from the cartridge;

FIG. 38 is a side elevational view in partial cross-section of thesurgical stapling apparatus of FIG. 17 illustrating the disengagement ofthe rack lock and pawl from the toothed rack by the release plate as theretraction knobs are pulled proximally to withdraw the actuation shaftand permit the anvil to move from the closed position shown in FIG. 37to an open position;

FIG. 39 is an enlarged side elevational view of the toothed rack and therelease plate associated therewith illustrating the rack lock engaged inthe toothed rack;

FIG. 40 is an enlarged side elevational view of the toothed rack and therelease plate associated therewith illustrating the release plate movedto disengage the rack lock from the toothed rack;

FIG. 41 is a cross-sectional view taken along line 41-41 of FIG. 39;

FIG. 42 is a cross-sectional view taken along line 42-42 of FIG. 40;

FIG. 43 is an enlarged perspective view of the rack lock (or engagementmember) illustrating the structural geometry thereof;

FIG. 44 is a side elevational view in partial cross-section of thedisposable loading unit illustrating the position of the axial driveassembly and control rod at the conclusion of a stapling procedure;

FIG. 45 is a side elevational view in partial cross-section of thedisposable loading unit of FIG. 24 with the components of the lockoutassembly illustrated in a position corresponding to the control rodbeing withdrawn toward a post-fired proximal position;

FIG. 46 is a side elevational view in partial cross-section of thedisposable loading unit of. FIG. 24 illustrating the orientation of thelockout assembly components as the control rod approaches itsproximal-most position;

FIG. 47 is a side elevational view in partial cross-section of thedisposable loading unit of FIG. 24 illustrating the orientation of thelockout assembly components when the control rod has been withdrawn toits proximal-most position;

FIGS. 48 is a side elevational view in partial cross-section of thedisposable loading unit of FIG. 24 illustrating the orientation of thelockout assembly components when the loading unit has been moveddistally with respect to the body portion to disengage the bayonetconnection;

FIG. 49 is a side elevational view in partial cross-section of thedisposable loading unit of FIG. 24 disengaged from the distal end of thebody portion at the conclusion of a stapling procedure with thecomponents of the lockout assembly illustrated in a blocking position toprevent subsequent utilization of the loading unit;

FIG. 50 is a cross-sectional view taken along line 50-50 of FIG. 46illustrating the relative positions of the blocking plate and controlrod prior to the removal of the disposable loading unit from the distalend of the body portion; and

FIG. 51 is an enlarged perspective view in partial cross-section of thedisposable loading unit after it has been removed from the distal end ofthe body portion illustrating the lockout assembly in a blockingposition to prevent entry of the distal end of the control rod into thedrive block of the axial drive assembly.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the drawings and in the description which follows, the term“proximal”, as is traditional, will refer to the end of the staplingapparatus which is closest to the operator, while the term “distal” willrefer to the end of the apparatus which is furthest from the operator.

Referring now to the drawings wherein like reference numerals identifysimilar structural elements of the subject invention, there isillustrated in FIG. 1 a surgical apparatus constructed in accordancewith a preferred embodiment of the subject application and designatedgenerally by reference numeral 10. In brief, surgical apparatus 10 is asurgical stapling apparatus configured to engage body tissue, apply aplurality of surgical fasteners thereto, and form an incision in thefastened body tissue during a laparoscopic surgical procedure. Apparatus10 can also be used to apply surgical clips and other fasteners(discussed in greater detail below) but will be primarily discussed inthe context of applying parallel rows of staples from a staple cartridgedisposed in a disposable loading unit.

Surgical apparatus 10 is unique among laparoscopic devices known in theart because it can employ a plurality of different sized disposableloading units. Moreover, apparatus 10 is preferably configured tooperate with individual disposable loading units that apply linear rowsof staples measuring 30 mm, 45 mm, or 60 mm in length (FIG. 1) or applyother types of fasteners (FIGS. 15 and 16). Thus, during a laparoscopicsurgical procedure, a single instrument can be utilized with a pluralityof interchangeable disposable loading units to perform several tasks.The preferred embodiments discussed in detail primarily relate todisposable loading units adapted to-apply linear rows of staples.

As illustrated in FIG. 1, surgical apparatus 10, has a handle assembly12 and an elongated body 14. Apparatus 10 is adapted for use withdisposable loading units 30, 45 and 60 each of which has a carrier 32, astaple cartridge 34, and an anvil 36 against which staples are drivenwhen ejected from their housing. The following specification willprovide a detailed description of the construction and operation of theapparatus and disposable loading units for use therewith.

Referring to FIG. 2, handle assembly 12 includes a housing 20 defined byan elongated barrel portion 22, a stationary handle 24 depending fromthe barrel portion, and an actuation handle 26 which is pivotablymounted to the barrel portion and movable with respect to the stationaryhandle. Actuation handle 26 is supported within housing 20 by a pivotpin 28 and is biased against counter-clockwise movement by a coiledtorsion spring 38.

Actuation handle 26 controls the linear movement of actuation shaft 40which is mounted within barrel portion 22. More particularly, actuationshaft 40 has a toothed rack 42 defined thereon, and actuation handle 26has a ratcheting pawl 44 mounted thereto for incrementally engaging andadvancing actuation shaft 40. Pawl 44 is mounted on a pivot pin 46 and acoiled torsion spring 48 biases the pawl into engagement with toothedrack 42. A linear biasing strut 50 is supported within barrel portion 22and is biased distally by a coiled compression spring 52 to bias thepawl, and hence the actuation handle, against clockwise rotation aboutpivot pin 28. Biasing strut 50 also serves to act on an angled rear camsurface on pawl 44 wherein contact of the cam surface with strut 50causes pawl 44 to rotate clockwise (away from rack 42). When theinstrument is at rest, pawl 44 is biased away from toothed rack 42. Whenactuation handle 26 is pulled proximally, pawl 44 moves away from strut50 and rotates counterclockwise and engages the teeth of actuation shaft40, thereby allowing actuation handle 26 to drive the shaft distally.

Actuation shaft 40 is normally biased in a proximal direction withinbarrel portion 22 by a constant force spring 54 which is mounted to theactuation shaft adjacent the distal end thereof by conventionalfastening means known in the art. Constant force spring 54 is supportedon a boss 56 provided within the housing 22 of handle assembly 12. Thedistal end portion of actuation shaft 40 has a cavity 58 defined in anundersurface thereof for engaging and retaining the flanged proximal end62 of control rod 64. Control rod 64 extends coaxially through theelongated body 14 of surgical stapler 10 to interact with a disposableloading unit at a distal end thereof. Thus, linear advancement ofactuation shaft 40 in response to manipulation of actuation handle 26causes corresponding longitudinal movement of control rod 64, and, aswill be discussed in detail hereinbelow, actuation of an associateddisposable loading unit.

With continuing reference to FIG. 2, the proximal end portion of theelongated body 14 of surgical stapler 10 has an annular flange 66 formedthereon which engages a corresponding annular recess 68 formed withinthe barrel portion 22 adjacent the distal end thereof to fixedly attachthe two structural members. The engagement of flange 66 within recess 68facilitates rotational movement of body portion 14 with respect to thebarrel portion 22 about a longitudinal axis which extends therethrough.A collar 70 is fixedly mounted to the proximal portion of stapler body14 by a pair of opposed protuberances 72 and 74. Thus, rotation ofcollar 70 will cause corresponding rotation of body portion 14 toincrease the range of operability of surgical stapler 10.

Within handle assembly 12, there is also contained a mechanism forinitiating the engagement between a rack lock 80 and the toothed rack 42of actuation shaft 40. Rack lock 80 maintains the longitudinal positionof actuation shaft 40 under the bias of constant force spring 54. Racklock 80 will not engage the rack unless and until a disposable loadingunit is operatively engaged in the distal end portion of portion body14. This mechanism is illustrated in FIG. 2 and its interaction withrack lock 80 is best understood by also referring to FIGS. 4 and 5. Themechanism includes an elongate beam or strut 82 having a distal tang84.that engages a keeper notch 86 formed adjacent the proximal end of asupport tube 88 that is slidably mounted within stapler body 14. Beam 82has a medial hook 90 for engaging the proximal end of a coiled biasingspring 92, the distal end of which is mounted on a boss 94 providedwithin barrel portion 22. Biasing spring 92 biases beam 82, and hencesupport tube 88, against proximal movement. An arcuate cam finger 96projects proximally from beam 82 for interacting with an angled camsurface 98 defined on the undersurface of the body 100 of rack lock 80.Rack lock 80 further includes a wedged clasp portion 102 which isdimensioned and configured to engage the teeth of the toothed rack 42 tomaintain the longitudinal position of actuation shaft 40 during theoperation of instrument 10. The body 100 of rack lock 80 is mounted on aboss 104 provided within the barrel portion 22 of housing 20. A coiledtorsion spring 106 is also mounted on boss 104 and is connected to body100 to bias the rack lock into engagement with toothed rack 42.

As best seen in FIGS. 4 and 5, when the proximal end portion of thecarrier 32 of disposable loading unit 30 is inserted into the distal endof elongated body 14, support tube 88 is urged in a proximal directionagainst the bias of spring 92. Thereupon, beam 82 translates proximallyand the arcuate cam finger 96 contacts angled cam surface 98, liftingrack lock 80 and causing it to rotate in a counter-clockwise directionagainst the bias of torsion spring 106. At such a time, the cam finger96 of beam 82 is accommodated within a recess 108 formed in the body 100of rack lock 80. With the rack lock in this position, it will engageactuation shaft 40 when it is advanced distally upon manipulation ofactuation handle 26. The interaction of rack lock 80 and actuation shaft40 will be discussed in greater detail hereinbelow with respect to themanner in which instrument 10 is operated to clamp body tissue and applyfasteners thereto.

Referring now to FIG. 3, an exemplary disposable loading unit isillustrated and is designated generally by reference numeral 30. Asnoted hereinabove, disposable loading unit 30, which is particularlyadapted to apply a plurality of linear rows of staples measuring about30 mm in length, is one of several different size or type of disposableloading units that can be utilized with instrument 10 during a surgicalprocedure. The carrier 32 of stapling unit 30 includes an elongatechannel 110 having a base 112 and two parallel upstanding walls 114 and116 which include several mounting structures for supporting staplecartridge 34 and anvil 36. Carrier 32 also includes mounting portion 120which is mounted to the proximal portion of channel 110 through theengagement of a plurality of spaced apart rectangular tangs 122 and aplurality of corresponding slots 124 formed in the opposed walls 114 and116 of channel 110. The proximal end section 126 of mounting portion 120is dimensioned and configured for insertion into the distal end portionof elongated body 14, and it is provided with an axial bore 125 foraccommodating the distal end of control rod 64.

A coupling stem 128 projects radially outwardly from end section 126 forinteracting with the J-shaped coupling slot 130 defined in the wall ofthe distal end portion of elongated body 14 (see FIGS. 4 and 5). Stem128 and slot 130 together define a conventional bayonet-type couplingwhich facilitates quick and easy engagement and removal of the staplingunit from the stapler during a surgical procedure. Once engaged in thedistal end portion of stapler elongated 14, the distal end-of supporttube 88 urges proximal end section 126 distally under the bias of coiledspring 92, thereby maintaining the coupling stem 128 within couplingslot 130.

With continuing reference to FIG. 3, the distal portion of channel 110supports staple cartridge 34 which contains a plurality of surgicalfasteners 132 and a plurality of corresponding ejectors or pushers 134that drive the fasteners from cartridge 34 under the influence of afastener driving force exerted by actuation sled 140. Staple cartridge34 is maintained within channel 110 by lateral struts 136 whichfrictionally engage the upper surfaces of channel walls 114 and 116, andthe frictional engagement of housing tabs, such as tab 138, withinnotches 139. These structures serve to restrict lateral, longitudinal,and elevational movement of the staple cartridge 34 within channel 110.

A plurality of spaced apart longitudinal slots 142 extend through staplecartridge 34 to accommodate the upstanding cam wedges 144 of actuationsled 140. Slots 142 communicate with a plurality of transverse retentionslots 146 within which the plurality of fasteners 132 and pushers 134are respectively supported. During operation, as actuation sled 140translates through staple cartridge 34, the angled leading edges of camwedges 144 sequentially contact pushers 136, causing the pushers totranslate vertically within slots 146, urging the fasteners 134therefrom. The result of the interaction between actuation sled 140 andpushers 136 is illustrated in FIGS. 12-14, and will be describedhereinbelow with reference thereto. See also, commonly assigned U.S.Pat. No. 4,978,049 to Green, the disclosure of which is hereinincorporated by reference in its entirety.

With continuing reference to FIG. 3, the anvil 36 of disposable loadingunit 30 is provided with opposed mounting wings 150 and 152 which aredimensioned and configured to engage pivot apertures 154 and 156 inchannel walls 114 and 116, respectively. A biasing member 158 havingspring arms 158 a and 158 b is secured to the proximal end of anvil 36.The spring arms bear against internal bearing surfaces defined withinmounting portion 120 to bias anvil 36 into a normally open positionwherein the interior fastener forming surface 155 thereof is spaced fromstaple cartridge 34.

Disposable loading unit 30 further includes an axial drive assembly 160for transmitting the longitudinal drive forces exerted by control rod 64to actuation sled 140 during a stapling procedure. Drive assembly 160includes an elongated drive beam 162 including a distal working head 164and a proximal engagement section 166. Engagement section 166 includes apair of engagement fingers 166 a and 166 b which are dimensioned andconfigured to mountingly engage a pair of corresponding retention slots168 a and 168 b formed in a drive block 168. Drive block 168 has aproximal porthole 170 for receiving the distal end of control rod 64when the proximal end of stapling unit 30 is inserted into the distalend of stapler body 14. Drive block 168 can be provided with an internalslot to receive a stem (not shown) from a distal end of control rod 64to form a bayonet type connection, similar to that shown in connectingelongated body 14 to coupling stem 128. Such a connection would enablethe user to manipulate drive beam 162 upon movement of control rod 64.The working end 164 of drive beam 162 is defined by a vertical supportstrut 172 which supports a knife blade 174, and an abutment surface 176which engages the central support wedge 145 of actuation sled 140. Knifeblade 174 travels slightly behind actuation sled 140 during a staplingprocedure to form an incision between the rows of staple body tissue. Aretention flange 178 projects distally from vertical strut 172 to retaina cylindrical cam roller 180. Cam roller 180 is dimensioned andconfigured to engage and translate with respect to the exterior cammingsurface 182 of anvil 36 to progressively clamp the anvil against bodytissue during firing.

A longitudinal slot 184 extends through anvil 36 to accommodate thetranslation of retention flange 178 and vertical strut 172. A balancingflange 186 is secured to the working end of drive beam 162 through theengagement of retention foot 188 within a complementary retention port190 formed in flange 186. Flange 186 serves to balance the clampingforces generated by cam roller 180 as anvil 36 is progressively clamped.A longitudinal slot 192 is formed in the base 112 of channel 110 toaccommodate the longitudinal translation of retention foot 188 duringfiring.

With reference to disposable loading unit 45 in FIG. 1, an anvil coveris provided to protect tissue from moving parts along the exterior ofanvil 36. In particular, anvil cover 400 has channel 402 formed on anunderside thereof and is secured to an upper surface of anvil 36 to forma channel therebetween. Cam roller 180 travels in channel 402 betweencover 400 and anvil 36 during firing. Anvil cover 400 is preferablyplastic, but can be fabricated from any suitable biocompatible material.

Returning to FIG. 3, dual constant force spring members 194 and 196 areconnected to the proximal end of channel base 112 and are disposeddistal of drive block 168 to bias the block against distal movement. Asbest seen in FIGS. 12-14, when drive block 168 translates distally,spring members 194 and 196 unwind until they are passed over by theblock at the end of its travel. At such a time, the spring membersreturn to their normally wound position providing a buffer for themounting block. Thus, an attempt to return the block to the proximalmost position after firing the disposable loading unit will beinhibited.

Referring now in sequential order to FIGS. 4-11, to initiate theoperation of instrument 10, a desired disposable loading unit isselected. Such disposable loading unit can be one of the different sizeddisposable loading units illustrated in FIG. 1 or one of the disposableloading units adapted to apply surgical clips (FIG. 15) or other typesof surgical staples (FIG. 16). Use of the instrument will be discussedherein using a disposable loading unit adapted to apply linear rows ofstaples. Disposable loading unit 30, is mounted to the stapler byinserting the proximal mounting section thereof into the distal end ofthe elongated body 14, as shown in FIG. 4. Prior to insertion, supporttube 88 is in its distal-most position within elongated body 14 and itis maintained in that position by spring 92. Accordingly, the cam finger96 of beam 82 maintains rack lock 80 in a disengaged uplifted position,spaced from the toothed rack 42 of actuation shaft 40.

Once the proximal end of the disposable loading unit is inserted intothe distal end of elongated body 14, it is rotated approximately 10° to15° to position coupling stem 128 in the base of coupling slot 130.Thereupon, the bias of spring 92 urges support tube 88 distally to lockstem 128 within the base of slot 130. If a coupling system is providedbetween control rod 64 and drive block 168 (discussed above) suchrotation would couple these member as well. In addition, as illustratedin FIG. 5, when support tube 88 is shifted proximally by the insertionof the proximal section 126 of mounting portion 120 into elongated body14, arcuate cam finger 96 of beam 82 translates proximally against camsurface 98 until it reaches recess 108. Thereupon rack lock 80 movesinto an engagement position under the bias of torsion spring 106, andinstrument 10 is ready for use.

Turning to FIG. 6, prior to utilization, actuation handle 26 is in theillustrated neutral position. In this position, pawl 44 is spaced fromthe toothed rack 42 of actuation shaft 40. In addition, lift arm 210which projects distally from actuation handle 26 is engaged beneath atransverse finger 212 formed at the proximal end of rack lock 80adjacent the wedged clasp portion 102. Lift arm 210 serves to disengageclasp portion 102 from actuation shaft 40 under certain operatingconditions which will be discussed hereinbelow with respect to FIGS. 8and 9.

Prior to manipulating actuation handle 26, actuation shaft 40 is in itsproximal-most position, as is control rod 64, biased against distalmovement by constant force spring 54. Accordingly, anvil 36 is in anopen position biased against closure by spring arms 158 a and 158 b.Thus, at such a time, body tissue such as tubular vessel 200 may becaptured between the fastener forming surface of anvil 36 and the tissuecontacting surface of staple cartridge 34.

Turning now to FIG. 7, manipulation of actuation handle 26 in thedirection indicated by reference arrow “A” causes pawl 44 move distallyand rotate counterclockwise to engage toothed rack 42 and driveactuation shaft 40 distally against the bias of spring 54. As a result,control rod 64 is driven distally, forcing drive block 168 forwardwithin disposable loading unit 30. Accordingly, a working end 164 ofdrive beam 162 translates distally and cam roller 180 engages theproximal end portion of the cam surface of anvil 36, causing the anvilto move into a closed position, clamping tubular vessel 200 against thetissue contacting surface of staple cartridge 34. In addition, whenactuation shaft 40 advances distally, the clasp portion 102 of rack lock80 engages a notched area 214 formed in the distal end portion ofactuation shaft 40 distal of toothed rack 42 under the bias of torsionspring 106. Thereupon, the longitudinal position of actuation shaft 40within barrel portion 22 is maintained, and anvil 36 is locked in aclosed position.

Under certain circumstances it may be necessary to open the anvil andunclamp the captured vessel or body tissue, i.e., to recapture thevessel at a different location. As illustrated in FIG. 8, to release theanvil, actuation handle 26 is manipulated in the direction indicated byreference arrow “B” against the bias of linear compression spring 52. Asa result, arm 210 lifts finger 212, rotating rack lock 80 in acounter-clockwise direction against the bias of torsion spring 106, asshown in FIG. 9. The clasp portion 102 of rack lock 80 is therebydisengaged from notched area 214, permitting actuation shaft 40 andcontrol rod 64 to return to their proximal-most positions. At such atime, drive block 168 moves proximally under the bias of spring members194 and 196. Accordingly, cam roller 180 is drawn off of the exteriorcamming surface 182 of anvil 36, and the anvil moves to an open positionunder the bias of spring member 158. Subsequent anvil closure isachieved in the manner described hereinabove with reference to FIG. 7.

Referring to FIG. 10, to fire instrument 10 and apply a plurality ofsurgical fasteners 132 to the tissue clamped between anvil 36 and staplecartridge 34, actuation handle 26 is manipulated toward stationaryhandle 24 in the direction indicated by reference arrow “C” against thebias of torsion spring 38. Thereupon, pawl 44 engages toothed rack 42and drives actuation shaft 40 distally against the bias of constantforce spring 54. In a preferred embodiment of firing a disposableloading unit having linear rows of staples, one complete stroke ofactuation handle 26 causes actuation shaft 40 to advance approximately15mm within barrel portion 22, urging drive beam 162 an equivalentdistance within disposable loading unit 30 as control shaft 64 transmitslongitudinal motion thereto. As a result, half of the surgical fasteners132 within 30 mm staple cartridge 34 are ejected therefrom upon movingactuation handle 26 one complete stroke. Actuation shaft 40 ismaintained in this longitudinally advanced position through theengagement of the clasp portion 102 of rack lock 80 and the toothed rack42. Subsequent release and movement of actuation handle 26 to a relaxedposition will therefore have no bearing on the longitudinal position ofactuation shaft 40.

To complete the staple firing operation, actuation handle 26 is onceagain approximated toward stationary handle 24, causing pawl 44 toengage toothed rack 42 and advance actuation shaft 40 in a distaldirection another 15 mm. Thus, two complete strokes of actuation handle26 causes actuation shaft 40 to advance 30 mm within barrel portion 22,urging the working end 164 of drive beam 162 through staple cartridge 34to sequentially eject all of the surgical fasteners therefrom. Ifdesired, the operator can incrementally advance control shaft 64 bymultiple short strokes, wherein the minimum advancement is dictated bythe linear distance between the teeth on rack 42. Therefore, while twocomplete strokes of the preferred stroke distance of 15 mm can be used(to fire a 30 mm disposable loading unit), complete strokes are notnecessary or required.

As best seen in FIGS. 12-14, two complete strokes of actuation handle 26causes actuation shaft 40 and the associated control rod 64 to translatefrom the proximal-most position illustrated in FIG. 12, wherein driveblock 168 is disposed adjacent the proximal end of channel 110, to thedistal-most position illustrated in FIG. 13, wherein drive block 168travels to the distal end of staple cartridge 34. During its travel,drive block 168 urges drive beam 166 distally, effectuating progressiveclosure of anvil 36 against tubular vessel 200, and sequential ejectionof surgical fasteners 132 into the body tissue as actuation sled 140travels through staple cartridge 34. As shown in FIG. 13, when camroller 180 reaches the distal end of its travel, it drops into thetransverse slot 185 formed at the distal end of anvil slot 184. As aresult, anvil 36 returns to an open position under the bias of springmember 158, releasing the stapled body tissue as illustrated in FIG. 14.Furthermore, spring members 194 and 196 rewind and return to a coiledcondition at the proximal end of channel 110.

At the conclusion of the above-described firing operation, disposableloading unit 30 is removed from the distal end of elongated body 14, asillustrated in FIG. 11. At such a time, support tube 88 is permitted toreturn to its distal-most position under the bias of spring 92.Accordingly, beam 82 translates distally causing arcuate cam finger 96to lift rack lock 80 out of engagement with the toothed rack 42 ofactuation shaft 40. As a result, actuation shaft 40 returns to itsproximal-most position within barrel portion 22 under the bias ofconstant force spring 54. Thereupon, a new disposable loading unit canbe joined with the instrument and another surgical task performed.

If the surgeon desires to apply parallel rows of staples each measuringabout 45 mm in length, disposable loading unit 45 (FIG. 1) is mounted tothe distal end portion of elongated body 14. After mounting, actuationhandle 26 is manipulated through a number of strokes equalling threecomplete actuation strokes to incrementally advance actuation shaft 40and control rod 64 a distance of 45 mm. Alternatively, if disposableloading unit 60 is selected for utilization to apply staple rowsmeasuring about 60 mm in length, actuation handle 26 must be manipulatedthrough a number of strokes equalling four complete actuation strokes toincrementally advance actuation shaft 40 and control rod 64 a distanceof 60 mm.

Turning to FIGS. 15 and 16, two alternate embodiments of disposableloading units are shown. Disposable loading unit 410 in FIG. 15 isdesigned to apply surgical clips. Disposable loading unit 410 has jawstructure 412 and a plurality of clips disposed in housing 414. Commonlyassigned U.S. Pat. No. 5,100,420, the disclosure of which is hereinincorporated by reference in its entirety, discloses a manner in whichclips can be fed to jaw structure 412 and formed. Disposable loadingunit 420 in FIG. 16 is designed to apply individual surgical staples,such as those useful during hernia repair. Disposable loading unit 420has jaw structure 422 and a plurality of staples disposed in housing424. Commonly assigned U.S. Pat. No. 5,289,963, the disclosure of whichis herein incorporated by reference in its entirety, discloses a mannerin which staples can be fed to jaw structure 422 and formed. Bothdisposable loading units 410 and 420 are secured to the surgicalinstrument in a manner similar to the disposable loading unitspreviously described and are actuated by the longitudinal motion ofactuation shaft 40 and control rod 64.

It is readily apparent and may be appreciated by those having ordinaryskill in the art that the stroke distance travelled by the actuationshaft may be adjusted in accordance with desired surgical practices. Forexample, it may be desirable to employ disposable loading units whichapply parallel staple rows measuring 40 mm, 60 mm, or 80 mm. Thus, theincremental stroke distance travelled by the actuation shaft could beadjusted to approximately 20 mm intervals. In addition, one skilled inthe art could provide alternate structure or orientation of structuresto control the advancement of control rod 64. For example, toothed rack42 could be rotated so the teeth face downward towards the handles andthe locks and pawls moved to engage the rack from the underside. Also,various safety mechanisms can be added, such as a lockout in the handlethat needs to be released prior to actually firing a disposable loadingunit. These and other features are described in greater detail, below.

Referring now to FIG. 17, there is illustrated another surgical staplingapparatus constructed in accordance with a preferred embodiment of thesubject application and designated generally by reference numeral 500.As in the previously described embodiment, surgical stapling apparatus500 is configured to engage body tissue, apply a plurality of surgicalfasteners thereto, and form an incision in the fastened body tissueduring a laparoscopic surgical procedure. The apparatus is preferablyconfigured to operate with individual disposable loading units thatapply linear rows of staples measuring 30 mm, 45 mm, or 60 mm in length(see generally FIG. 1), or other types of disposable loading units (see,generally FIGS. 15 and 16).

As illustrated in FIG. 17, surgical stapler 500 has a handle assembly512 and an elongated body 514, and is adapted for use with a disposableloading unit 530, among other units not shown, which has a carrier 532,a staple cartridge 534, and an anvil 536 against which staples aredriven when ejected from the cartridge.

Referring to. FIG. 18, as in the previous embodiment, handle assembly512 includes a housing 520 defined by a barrel portion 522, a stationaryhandle 524, and a pivoting actuation handle 526. Actuation handle 526 issupported in housing 520 by pivot pin 528 and is biased away fromstationary handle 524 by a torsion spring 538. Actuation handle 52.6controls the linear movement of actuation shaft 540 which is supportedwithin the barrel portion 522 of housing 520. More particularly,actuation shaft 540 has a toothed rack 542 defined on an undersurfacethereof and actuation handle 526 is provided with a pawl 544 which ismounted to selectively engage toothed rack 542 and advance the actuationshaft 540 in a distal direction in response to manipulation of actuationhandle 526 through an actuating stroke. Pawl 544 is mounted to actuationhandle 526 by a pivot pin 546 and is biased toward toothed rack 542 by acoiled torsion spring 548. The mounting portion of pawl 544 is curved tointeract with an abutment wall 545 defined within the housing 520 ofhandle assembly 512. More particularly, when the curved mounting portionof pawl 544 contacts abutment wall 545, the pawl is rotated out ofengagement with the toothed rack 542 of actuation shaft 540.

Actuation shaft 540 is normally biased in a proximal direction withinbarrel portion 522 by a constant force spring 554 which is supported ona boss 556 provided within housing 520. A notched area 555 is formed inthe upper surface of actuation shaft 540 adjacent the proximal endthereof for receiving and retaining an engagement tab 557 provided atthe free end of constant force spring 554. The distal end of actuationshaft 540 is provided with a catchment fitting 558 for engaging theflanged proximal end 564 p of control rod 564. Control rod 564 extendsfrom the handle assembly 512 through the elongated body portion 514 tointeract with the disposable loading unit 530 supported at the distalend of the body portion. Accordingly, manipulation of actuation handle526 causes corresponding longitudinal translation of the actuation shaft540 and control rod 564 to actuate the disposable loading unit in amanner which will be discussed in detail hereinbelow.

With continuing reference to FIG. 18, the proximal end of the elongatedbody portion 514 of surgical stapler 500 has an annular flange 566formed thereon which is received in a corresponding annular recess 568formed within the barrel portion 522 adjacent the distal end thereof.This connection facilitates rotational movement of body 514 relative tohandle assembly 512 about a longitudinal axis extending therethrough. Acollar 570 is fixedly mounted to body portion 514 by at least oneprotuberance 572 to effectuate the axial rotation of body portion 514and thereby increase the operational range of surgical stapler 500.

As in the previously described embodiment, surgical stapler 500 includesa rack lock (or engagement member) 580 which interacts with the toothedrack 542 of actuation shaft 540 to selectively maintain the longitudinalposition thereof within barrel portion 522 against the bias of constantforce spring 554. Rack lock 580 is mounted in such a manner so as tomove into a position to interact with toothed rack 542 only when adisposable loading unit has been inserted into the distal end of bodyportion 514. More particularly, rack lock 580, which is mounted on apivot pin 583 and biased toward the toothed rack 542 by a coiled torsionspring 585, is maintained in a non-interactive position by an abutmentstrut 582 until a disposable loading unit is loaded into the device.Abutment strut 582 is mounted on a securement flange 586 formed at theproximal end of a support tube 588 which is mounted for axialtranslation within body portion 514 (see FIG. 21).. A coiled biasingspring 592 connects abutment strut 582 to a boss 593 in the housing 520of handle assembly 512, and, in effect, biases the support tube 588 in adistal direction so that upon insertion of a disposable loading unit,support tube 588 and abutment strut 582 are shifted in a proximaldirection.

More specifically, as illustrated in FIG. 22, prior to insertion ofloading unit 530, an arcuate camming finger 596 which projectsproximally from abutment strut 582 is in contact with a distal portionof an angled camming surface 598 defined on rack lock 580. At such atime, rack lock 580 is maintained in a non-interactive position againstthe bias of coiled torsion spring 585. Thereafter, as shown in FIG. 23,when loading unit 530 is inserted into the distal end of body portion514 and rotated to engage the bayonet connection associated therewith(stems 628 a and 628 b, slots 630 a and 630 b), support tube 588 andabutment strut 582 are urged proximally against the bias of coiledspring 592 (and coiled spring 597). As a result, the proximal cammingfinger 596 translates in a proximal direction along camming surface 598,permitting rack lock 580 to rotate about pin 583 under the bias oftorsion spring 585 into an interactive position in which the toothedrack 542 of actuation shaft 540 may be engaged upon the distaltranslation thereof.

As illustrated in FIGS. 22 and 23, a second abutment strut 584 isdisposed opposite abutment strut 582 and is connected to the proximalend of support tube 588 in the same manner as abutment strut 582.Abutment strut 584, and the spring 597 which is associated therewith andconnected to housing 520 by boss 591, provide additional biasing forceto securely maintain the bayonet connection between the disposableloading unit 530 and the body portion 514.

Referring to FIG. 19, an elongated slot 602 extends along a portion ofsupport tube 588 and a transverse groove 604 extends along the axialbore 606 of body portion 514 to accommodate a support pin 608 whichextends radially outwardly from the central portion of control rod 564.This connection permits longitudinal movement of support tube 588 withrespect to body portion 514 and control rod 564 while maintaining therespective angular orientation of the three coaxial structures tofacilitate their axial rotation by collar 570.

Turning now to FIG. 24, there is illustrated disposable loading unit 530which is constructed in a manner that is substantially similar to theloading unit illustrated in FIG. 3. It includes a carrier 532 having anelongated support channel 610 for supporting staple cartridge 534 andanvil 536 and a mounting portion 620 which is configured for releasableengagement in the distal end of body portion 514. More particularly, theproximal end portion 626 of mounting portion 620 is provided with a pairof coupling stems 628 a and 628 b which interact with the J-shapedcoupling slots 630 a and 630 b formed at the distal end of body portion514 (see, for example, FIG. 26). The coupling stems and J-shaped slotstogether define the conventional bayonet-type coupling which facilitatesthe engagement and removal of the loading unit from the stapler. As inthe previous embodiment, an axial bore 625 extends through the proximalend 626 of mounting portion 620 to receive the distal end portion 564dof control rod 564.

As in the previous embodiment, disposable loading unit 530 includes anaxial drive assembly 660 which, among other things, transmits thelongitudinal drive forces exerted by control rod 564 to the actuationsled 640 disposed within the spaced apart longitudinal slots 642 thatextend through staple cartridge 534. A plurality of staple pushers 643are operatively associated with slots 642 and are sequentially contactedby actuation sled 640 as it is driven through staple cartridge 534 bydrive assembly 660. The staple pushers interact with the plurality ofstaples housed within staple cartridge 534 to sequentially eject thestaples therefrom.

Drive assembly 660 includes a bifurcated drive beam 662 having a distalworking head 664 and a proximal engagement section 665 that includes apair of engagement fingers 666 a and 666 b (see FIG. 25) configured tomountingly engage a drive block 668. Drive block 668 has a proximalporthole 670 for receiving the distal end 564 d of control rod 564 whenthe proximal mounting portion 626 of loading unit 530 is inserted intothe distal end of elongated body portion 514, as illustrated, forexample, in FIG. 27.

Referring to FIG. 20, the distal end portion 564 d of control rod 564 isformed with a flange 667 having a pair of diametrically opposed notches669 a and 669 b dimensioned to accommodate the two opposed engagementfingers 666 a and 666 b when the control rod is received in the proximalportal 670 of drive block 668, as best seen in FIGS. 26 and 29.Thereafter, as illustrated in FIGS. 28 and 30, when loading unit 530 isrotated through approximately a 20° axial turn to engage coupling stems628 a and 628 b within J-shaped coupling slots 630 a and 630 b,engagement fingers 666 a and 666 b are moved out of alignment withengagement notches 669 a and 669 b, and flange 667 is secured fromexiting disposable loading unit 530 until its removal from surgicalstapler 500. As seen when comparing FIGS. 27 to FIG. 28, the interiorcavity 671 of drive block 668 is dimensioned to accommodate theeextension of the distal portion 564 a of control rod 564 into portal 670during the insertion of the loading unit 530 into the distal end of bodyportion 514.

Referring again to FIG. 24, the working head 664 of drive assembly 660is defined in part by vertical support strut 672 which supports a knifeblade 674, and defines an abutment surface 675 for engaging actuationsled 640. A retention flange 678 projects distally from support strut672 to retain a cam roller 680 which is configured to translate alongthe exterior camming surface 682 of anvil 536 during a staplingprocedure to effect closure of the anvil against the bias of anvilspring 676. A longitudinal slot 684 extends through anvil 536 toaccommodate the translation of retention flange 678, and a similar slot692 is formed in the base 612 of channel 610 to accommodate thetranslation of retention foot 688 which supports balancing flange 686.Flange 686 serves to balance the clamping forces exerted by cam roller680 on anvil 536. As in the previous embodiment, an anvil cover (notshown) can be provided to protect tissue from contacting componentstraveling along the exterior surface 682 of anvil 536 during a staplingprocedure.

Referring to FIGS. 24 and 25, disposable loading unit 530 is providedwith a lockout assembly 700 configured to operate in two distinctstages. In brief, during the first stage of operation, the lockoutassembly functions to limit the longitudinal movement of control rod 564with respect to the axial drive assembly 660 (see FIG. 46). In thesecond stage of operation, i.e., after the disposable loading unit hasbeen removed from the apparatus following a stapling procedure, thelockout assembly serves to prevent subsequent utilization of the loadingunit by blocking the entry of control rod 564 into the proximal portal670 of drive block 668 (see FIG. 51).

As best seen in FIG. 25, preferred lockout assembly 700 includes ablocking plate 710 having a pair of parallel support arms 712 a and 712b which depend distally therefrom. A central aperture 716 is formed inblocking plate 710 which is dimensioned and configured to accommodatethe longitudinal translation of control rod 564. Aperture 716 includesdiametrically opposed slots 717 a and 717 b to accommodate theengagement fingers 666 a and 666 b of the proximal portion 665 ofactuation beam 662. A retention spring 718 is connected to blockingplate 710 through the engagement of a pair of spaced apart tabs 720 aand 720 b with a pair of corresponding ports 722 a and 722 b. Retentionspring 718 includes a mounting flange 724 for securing the spring to amounting area 725 on the interior surface of the mounting portion 620 ofdisposable loading unit 530 (see FIG. 26). The proximal end portion ofretention spring 718 is defined by a pair of spaced apart camming ramps726 a and 726 b which are angled proximally to interact with the distalflange 667 of control rod 564 when disposable loading unit 530 isremoved from the apparatus (see generally FIG. 47).

Lockout assembly 700 further includes a support plate 730 having a pairof depending arms 732 a and 732 b which interact with the support arms712 a and 712 b of blocking plate 710 to maintain the blocking plate ina non-blocking position against the bias of retention spring 718 (seeFIG. 26). Support plate 730 is formed with a central slotted region 733which accommodates the lower portion of drive beam 662. A detent 734 isformed within slotted region 733 for interacting with distal andproximal complementary recesses 735 a and 735 b formed in the lowerportion of drive beam 662.

In use, when drive beam 662 is driven distally, as shown for example inFIG. 44, support plate 730 is drawn therewith through the engagement ofdetent 734 with proximal recess 735 b. As a result, blocking plate 710is released and translates in a direction transverse to the longitudinalaxis of control rod 564 under the bias of retention spring 718. As shownfor example in FIG. 45, while control rod 564 is extending throughaperture 716, blocking plate 710 remains in a non-blocking position.However, when control rod 564 is fully retracted to open anvil 536 aftera stapling procedure, blocking plate 710 moves into a limiting position,engaging the distal portion 564 d of control shaft 564, as illustratedin FIG. 46. In this position, blocking plate 710 effectively limits therange of longitudinal motion of control rod 564, the range being definedby the reduced diameter portion at the distal end of control rod 564.

Upon full withdrawal of flange 667 from drive block 668, blocking plate710 is free to translate into a full blocking position under the bias ofretention spring 718 to block the proximal portal 670 of drive block668, as illustrated in FIG. 49. The function of lockout assembly 700 andits interaction with control rod 564 and axial drive assembly 660 willbe discussed in further detail hereinbelow.

Referring now in sequential order to FIGS. 31-38, to initiate operationof surgical stapler 500, a desired disposable loading unit of aparticular size and kind is selected from a group of different units andloaded into the distal end of body portion 514. The loading unit, i.e.,loading unit 530, is mounted to stapler 500 by inserting the proximalmounting portion 626 into the distal end of body portion 514 androtating the unit to securely engage the bayonet connection (see FIGS.22 and 23). A preferred degree of rotation is between about 5° and about40°, while about 20° is most preferred. At such a time, support tube 588is urged proximally from the position shown in FIG. 22 to that which isillustrated in FIG. 23. As a result, rack lock 580 is moved into aninteractive position shown in FIG. 31, wherein the toothed rack 542 ofactuation shaft 540 may be engaged upon the distal advancement thereof.As illustrated in FIG. 31, when actuation shaft 540 is in itsproximal-most position biased by constant force spring 554, anvil 536 isin an open position to receive body tissue such as tubular vessel 750.At such a time, pawl 544 is engaged in the distal-most tooth on toothedrack 542 and actuation handle 526 may be manipulated against the bias ofspring 538 to advance the toothed rack.

As best seen in FIG. 32, upon initial manipulation of actuation handle526 through a first segment of the actuation stroke (i.e., the clampingstroke segment), actuation shaft 540 is driven in a distal direction bythe interaction of pawl 544 and toothed rack 542. Thereupon, theengagement hook 752 of rack lock 580 engages a keeper notch 754 formedadjacent the distal fastening portion 558 of actuation shaft 540. Atsuch a time, anvil 536 is moved to a closed position by the advancementof cam roller 680 along the proximal camming portion of anvil surface682, and the proximal end of engagement hook 752 is in abutment with abuttress 755 formed on the under surface of actuation shaft 540. As aresult, further distal translation of actuation shaft 540 is prohibitedand anvil 536 is maintained in a clamped position.

If, at a such a time, the user of the apparatus desires to unclamptubular vessel 750 by opening anvil 536, this can be accomplishedthrough the manipulation of a retraction mechanism (described below)associated with handle assembly 512 which serves to disengage rack lock580 and pawl 544 from actuation shaft 540 to permit the user to draw theactuation shaft in a proximal direction, as illustrated in FIG. 33.

Referring back to FIG. 18, the retraction mechanism preferably includesa pair of retractor knobs 760 a and 760 b which are connected to theproximal end of actuation shaft 540 by a coupling rod 762. Coupling rod762 includes right and left engagement portions 764 a and 764 b forreceiving retractor knobs 760 a and 760 b and a central portion 764cwhich is dimensioned and configured to translate within a pair oflongitudinal slots 766 a and 766 b formed in actuation shaft 540adjacent the proximal end thereof. A release plate 768 is operativelyassociated with actuation shaft 540 and is mounted for movement withrespect thereto in response to manipulation of retractor knobs 760 a and760 b. More particularly, a pair of spaced apart pins 767 a and 767 bextend outwardly from a lateral face of actuation shaft 540 to engage apair of corresponding angled cam slots 769 a and 769 b formed in releaseplate 768. The cam slots define the path through which the release platemoves with respect to the actuation shaft 540, and more specifically,with respect to the toothed rack 542. A transverse slot 770 is formed atthe proximal end of release plate 768 to accommodate the central portion760 c of coupling rod 762, and elongated slots 772 and 774 are definedin the barrel section 522 of handle assembly 520 to accommodate thelongitudinal translation of coupling rod 762 as retraction knobs 760 aand 160 b move in conjunction with actuation shaft 540. Coupling rod 762is biased distally by spring 765 a which is secured at ine end tocoupling rod portion 764 c and at the other end to post 765 b onactuation shaft 540.

Referring again to FIG. 33, when it is desirable to open anvil 536 torelease the clamped body tissue 750, the user of apparatus 500 pullsretraction knobs 760 a and 760 b proximally, whereupon release plate 768translates in a generally proximal direction along the path of angledcam slots 769 a and 769 b (see generally FIGS. 39 and 40). Consequently,the release plate urges the engagement hook 752 of rack lock 580 out ofkeeper notch 754 an forces pawl 544 out of engagement with toothed rack542. At such a time, the user can draw actuation shaft 540 in a proximaldirection, causing cam roller 680 to be drawn proximally with actuationbeam 662. As a result, anvil 536 moves to an open position under thebias of anvil spring 676 and actuation handle 526 returns to a neutralposition under the bias of torsion spring 538. Once actuation shaft 540has been returned to its proximal-most position, stapling apparatus 500is in a reset condition.

Referring now to FIG. 34, to clamp body tissue 750 once again, actuationhandle 526 is manipulated through the clamping segment of an actuationstroke to drive actuation shaft 540 distally until the engagement hook752 of rack lock 580 is once again engaged in keeper notch 754 and inabutment with buttress 755. If, at such a time, the user of apparatus500 is confident that the stapling procedure can commence, rack lock 580must be manually released from keeper notch 754 to permit subsequentdistal movement of actuation shaft 540. This is accomplished by way of amanual release mechanism operatively associated with handle assembly 512which interacts with the proximal release tail 757 of rack lock 580, asshown in FIG. 35. The details of a preferred construction of rack lock(or engagement member) 580 are illustrated in FIG. 43.

Referring back once again to FIG. 18, the manual release mechanismpreferably includes a pivoting release member 780 mounted on a boss 784and biased away from the release tail 757 of rack lock 580 by a coiledtorsion spring 786. A pair of opposed winglets, i.e., winglet 788,project laterally from release member 780 to support release knobs 790 aand 790 b, respectively. Release member 780 has a downturned nose 792which is dimensioned to contact the release tail 757 of rack lock 580when release knobs 790 a and 790 b are manipulated by the user in thedirection indicated by arrow “A” in FIG. 35.

Referring once again to FIG. 35, upon manipulation of release knobs 790a and 790 b and the consequential liberation of rack lock 580, actuationshaft 540 is free to translate in a distal direction in response tomanipulation of actuation handle 526. At such a time, the linearposition of actuation shaft 540 is maintained through the engagement ofpawl 544 and toothed rack 542.

Turning to FIG. 36, manipulation of actuation handle 526 towardstationary handle 524 through a stapling stroke segment causes pawl 544to advance toothed rack 542, and hence actuation shaft 540 and controlrod 564, in a distal direction. As a result, the axial drive assembly660 supported within loading unit 530 is driven distally to causeactuation sled 640 to intersect with pushers 643 to sequentially ejectstaples from cartridge 534. At the same time, knife blade 674 travelsbehind actuation sled 640, forming an incision in the stapled bodytissue. As shown in FIG. 36, one complete stapling stroke effects firingof only a portion of the staples within cartridge 534. As previouslydescribed, multiple partial strokes can also be used to incrementallyadvance drive rod 564, i.e. pawl 544 can advance rack 542 one tooth at atime.

Referring to FIG. 37, all of the staples within cartridge 534 areejected and applied to tubular vessel 750. If a loading unit having agreater length had been employed with stapling apparatus 500, additionalstapling strokes would have been required to advance actuation shaft 540further. In total, the toothed rack 542 of actuation shaft 540 ispreferably dimensioned to accommodate at least four complete staplingstrokes of 15 mm each. Thus, if each complete stapling stroke ofactuation handle 526 advances the actuation shaft 15 mm, staplingapparatus 500 can be used to fire disposable loading units that areconfigured to apply staple lines of 15 mm, 30 mm, 45 mm, and 60 mm usinga whole number of complete strokes.

Referring now to FIG. 38, at the conclusion of the stapling procedure,to move anvil 536 to an open position and release stapled body tissue750 from surgical apparatus 500, the user once again employs theretraction knobs 760 a and 760 b associated with the barrel portion 522of handle assembly 520. More particularly, as best seen in FIGS. 39-42proximal retraction of knobs 760 a and 760 b causes coupling rod 762(FIG. 18) to translate proximally within the longitudinal slots 766 aand 766 b formed at the proximal end of actuation shaft 540. As aresult, release plate 768 translates along an angled path defined by camslots 769 a and 769 b, urging the engagement hook 752 of rack lock 580and the pawl 544 (not shown) out of engagement with toothed rack 542.Thereupon, as illustrated in FIG. 38, actuation shaft 540 is free totranslate in a proximal direction under the bias of the user andconstant force spring 554. Consequently, the axial drive assembly 660within disposable loading unit 530 is drawn proximally by the head ofcontrol rod 564, and anvil 536 moves to an open position as cam roller680 is retracted.

Referring now to FIG. 45, as control rod 564 is withdrawn in a proximaldirection from its distal-most position illustrated in FIG. 44, blockingplate 710 rides along control rod 564 and is maintained in an uprightposition against the bias of retention spring 718. However, asillustrated in FIG. 46, as reduced diameter distal end portion 564 d ofcontrol rod 564 approaches its proximal-most position, blocking plate710 is urged toward the control rod such that the peripheral edge ofaperture 716 engages distal end portion 564 d of control rod 564 (seealso FIG. 50). Further proximal movement of control rod 564 draws driveblock 668 to its proximal-most position illustrated in FIG. 47, whereinflange 667 interacts with camming ramps 762 a and 762 b of retentionspring 718 and at least partially lifts blocking plate 710. At such atime, distal movement of control rod 564 is limited due to interactionbetween blocking plate 710 and the larger diametered ledge where theproximal end of 564 d meets the larger diameter of rod 564. However,control rod 564 is still afforded a limited range of longitudinal motionalong reduced diameter portion 564 d of control rod 564 so that anvil536 can be moved between open and closed positions. Accordingly, anvil536 may be easily closed to facilitate removal of surgical apparatus 500through a trocar or cannula device.

As best seen in FIG. 47, when axial drive assembly 660 and the driveblock 668 associated therewith assume their proximal-most position, thedetent 734 on support plate 730 engages distal recess 735 a. At such atime, support plate 730 is securely retained in its final rest positionto prevent the plate from floating within disposable loading unit 530after it has been removed from surgical apparatus 500.

Referring to FIG. 48, to remove disposable loading unit 530 from thedistal end of body portion 514, the loading unit is shifted proximallyand rotated to disengage the bayonet coupling. Simultaneously, theengagement fingers 666 a and 666 b are re-aligned with the notches 669 aand 669 b in flange 667. The flange can now further bias locking plate710 upward, allowing for the removal of disposable loading unit 530 fromthe distal end of body portion 514. As soon as flange 667 moves pastcamming ramps 762 a and 762 b and blocking plate 710, the blocking plateis free to translate into a full blocking position under the bias ofretention spring 718. In this position, which is best seen in FIG. 51,entry of the distal end of control rod 564 into the proximal portal 670of drive block 668 is advantageously prohibited. Accordingly, a fired orpartially fired disposable loading unit cannot be subsequently utilizedafter it has been removed from surgical apparatus 500.

Although the subject invention has been described with respect topreferred embodiments, it will be readily apparent to those havingordinary skill in the art to which it appertains that changes andmodifications may be made thereto without departing from the spirit orscope of the subject invention as defined by the appended claims.

1. A surgical stapler comprising: a) a handle assembly including apivotable handle mounted for manipulation through at least one actuatingstroke; b) an elongated body extending distally from the handle assemblyand defining a longitudinal axis; c) a channel disposed adjacent thedistal end of the elongated body; d) a staple cartridge configured anddimensioned to be supported by the channel, the staple cartridgecontaining a plurality of staples; e) an anvil pivotally mounted inrelation to the cartridge adjacent the distal end of the elongated body,the anvil having a fastener forming surface thereon and being mountedfor pivotal movement in relation to the cartridge; f) an actuation sledpositioned in the staple cartridge, the actuation sled being movable toeject the plurality of staples from the staple cartridge; g) a driveassembly including a drive member having a working end and a cam memberon the working end, the cam member being positioned to engage the anvilto effectuate progressive closure of the anvil against tissue, thepivotable handle being operably connected to the drive assembly suchthat manipulation of the pivotable handle through at least one actuatingstroke effects translation of the cam member relative to the anvil; andh) a flange member supported at the working end of the drive member, theflange member being positioned to engage the channel.
 2. A surgicalstapler according to claim 1, wherein the actuation sled includes aplurality of cam surfaces and is movable through the staple cartridge tourge the plurality of staples from the staple cartridge.
 3. A surgicalstapler according to claim 2, wherein the working end of the drivemember is positioned to abut the actuation sled to effect translation ofthe actuation sled through the staple cartridge.
 4. A surgical stapleraccording to claim 3, wherein the staple cartridge includes a pluralityof spaced apart retention slots, each of the retention slots supportingone of the plurality of staples.
 5. A surgical stapler according toclaim 1, wherein the drive assembly includes a rack and the pivotablehandle includes a pawl configured to engage the rack to advance thedrive member in response to manipulation of the pivotable handle.
 6. Asurgical stapler according to claim 1, wherein the anvil includes ananvil cover that defines a channel, the cam member traveling in thechannel.
 7. A surgical stapler according to claim 1, wherein the flangemember engages the channel to balance clamping forces generated by thecam member as the anvil is progressively closed.
 8. A surgical stapleraccording to claim 1, wherein the drive member supports a knife blade atthe working end.
 9. A surgical stapler according to claim 8, wherein thedrive member has a surface for abutting the actuation sled in thecartridge, the actuation sled causing staples to be driven from thecartridge.
 10. A surgical stapler comprising: a) a handle assemblyincluding a pivotable handle mounted for manipulation through at leastone actuating stroke; b) an elongated body extending distally from thehandle assembly and defining a longitudinal axis; c) a channel disposedat the distal end of the elongated body; d) a staple cartridgeconfigured and dimensioned to be supported by the channel, the staplecartridge containing a plurality of staples arranged in a plurality ofrows and at least one slot disposed between the rows of staples; e) ananvil pivotally mounted in relation to the cartridge adjacent the distalend of the elongated body, the anvil having a fastener forming surfacethereon; f) an actuation sled positioned in the staple cartridge, theactuation sled being movable through the cartridge to cooperate withstaple pushers to eject the plurality of staples from the staplecartridge; g) a drive assembly including a drive beam having an anvilengaging member and a balancing flange, the pivotable handle beingoperably connected to the drive assembly such that manipulation of thepivotable handle through at least one actuating stroke effectstranslation of the drive beam through the staple cartridge slot, wherebythe balancing flange and the anvil engaging member together effectprogressive clamping of the anvil and cartridge and advancement of theactuation sled through the staple cartridge.
 11. A surgical stapleraccording to claim 10, wherein the actuation sled includes a pluralityof cam surfaces.
 12. A surgical stapler according to claim 10, whereinthe drive beam has a surface positioned to abut the actuation sled toeffect translation of the actuation sled through the staple cartridge.13. A surgical stapler according to claim 10, wherein the drive assemblyincludes a rack and the pivotable handle includes a pawl configured toengage the rack to advance the drive beam in response to manipulation ofthe pivotable handle.
 14. A surgical stapler according to claim 10,wherein the anvil includes an anvil cover that defines an anvil channel,the anvil engaging member translating through the anvil channel duringthe actuating stroke.
 15. A surgical stapler according to claim 10,wherein the balancing flange engages the channel to balance clampingforces generated during progressive clamping of the anvil and cartridge;16. A surgical stapler according to claim 10, wherein the drive beamsupports a knife blade.
 17. A surgical stapler according to claim 16,wherein the drive beam includes a strut and the knife blade is supportedby the strut, such that the knife blade translates through the cartridgeslot during the actuating stroke.
 18. A surgical stapler according toclaim 10, wherein the anvil engaging member is a cam.